Imaging your sample is a powerful way to better understand how the properties of materials alter with changing environmental conditions. Linkam has always understood this and offers a range of optional imaging modules to meet various experimental requirements.
Many materials change in colour, shape and size with varying conditions. For example, thermotropic liquid crystals undergo phase transitions as the temperature is changed, rubber can tear when under tensile force and many materials change colour as they oxidise at higher temperatures. By acquiring images as well as recording the sensor parameters, visual changes can be analysed, the crack velocity of a fracturing material can be tracked, the size and shape of particles can be measured, and all these changes correlated with temperature.
In order to provide the best performance, we have upgraded our high-performance Image Capture module to include a new 3.2Mp camera. When combined with our LINK Core software package and Image Capture module, the new camera provides an integrated imaging solution. This enables image capture synchronised with precise temperature control of your sample and correlated with other controlled and measured parameters. Combining these imaging tools with one of our temperature control stages provides a powerful sample characterisation platform across a broad range of applications, including geology, materials science, pharmaceuticals and semiconductor research, as shown in the examples below:
Geology
Geological and earth scientists have always been challenged to understand the evolution of mineral samples with changing atmospheric conditions. Better knowledge of the behaviour of natural mineral deposits and fluid inclusions deepens the understanding of the earth’s historical geological behaviour. In this example, researchers in Beijing, China are looking at the size and composition of various inclusions and minerals including CO₂-rich and salt/water inclusions in quartz (pictured below), stibnite, wolframite and pyrite. Using a Linkam THMSG600, they were able to identify how much the temperature deviated during microthermometric measurements due to “warming” from IR light. They have discovered that transparent and translucent minerals absorb more IR energy, and thus a greater effect on phase transition temperatures was seen. Read the full article here.
Microscope image of CO₂-rich fluid inclusions in a natural quartz specimen from the Beijing region in China observed using Linkam’s THMSG600 Geology stage
Polymer crystallisation under shear
In another example, researchers in the Polymer Technology Group of the Department of Chemical and Food Engineering at the University of Salerno, Italy captured images of isotactic polypropylene while the material underwent shear stress in order to study the phenomenon of flow-induced crystallisation. Using images from these video sequences (as seen in the figure below), they were able to quantitatively determine the crystal nucleation rate under different shear conditions and temperatures. They found that nucleation improved under continuous shearing and increased as a function of shear rate. Furthermore, they found that nucleation density decreases on increasing the crystallisation temperature. Read more about their study here.
Micrographs of isotactic polypropylene (iPP) collected during the crystallization test under shear conditions at 140°C and shear rate of 0.11 s⁻¹ at different shearing times using Linkam’s CSS450 Shear stage
Tensile testing of adhesive films
There are other reasons to study the visual properties of materials undergoing mechanical forces as a function of temperature. For example, tensile testing can be used to reveal the properties of thin films used for flexible electronic devices, such as these polyethylene napthalate (PEN) thin films. In this work the researchers stretched thin PEN films, adhered to ITO coatings, up to very high stress levels and temperatures up to 150°C. This allowed them to simulate the environmental factors these films should be able to withstand throughout the life of the flexible devices they will be used in. By imaging the samples under strain and at elevated temperature (seen in the figure below), they found that the adhesion of PEN to the ITO coating was dependent on temperature due to a softening of the polymer substrate. They were able to quantify the crack density – indicative of the material failure – using the images taken during the experiment. Read the full report here.
Tensile curves of polyethylene naphthalate (PEN) at 23°C (a) and at 150°C (b). Optical micrographs of these samples taken at 18% strain at 23°C (c) and 150°C (d), showing crack density at saturation for ITO/PEN samples. The micrographs were taken with a green filter to emphasize contrast, and the loading direction was parallel to the scale bar in the micrographs using Linkam’s TST350 tensile stage (now replaced by the new MFS stage).
LINK supports a number of modules to optimise image-based sample characterisation, incuding the LINK Image Capture module, the LINK Extended Measurements module and TASC (Thermal Analysis by Structural Characterisation), which bring image analysis to many Linkam stages. Contact us for more information about imaging with temperature controlled microscopy.
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